B450-PLUS seems to work as well, running now with 2x KSM26ES8/8ME. I could see no mention of 6-layers PCB on Asus or Asrock or Gigabyte web so I just went with the Asus.
DMI: System manufacturer System Product Name/PRIME B450-PLUS, BIOS 1201 04/25/2019
smpboot: CPU0: AMD Ryzen 5 PRO 3400G with...